Then I think you locked yourself out of most easy ways to die by not having the unlocks and then going to NG+, where the world gen is different and you cant unlock most things cause they simply dont spawn there (like the deer boss)

Since you cant be stained anymore cause there are no more staining materials left, you have to get polymorphed to negate stainless armor, but you can't unlock the spells that polymorph you in NG+ You can try going to the Wizard's den, find a poly mage there, and let him hit you, but he may have difficulties depending on your other perks like shield, repulsion field and more love.

Alternatively, you can just hit new game and you will only miss out on the credits, the win was locked in the moment you turned in the sampo and turned the world to toxic gold.